In the drilling, completion, and stimulation of oil and gas wells, well treatment fluids are often pumped into well bore holes under high pressure and at high flow rates causing the rock formation surrounding the well bore to fracture. As the fluid is pumped through the pipe at high flow rates (thousands of GPM) there is a significant amount of frictional resistance, which results in large energy requirements.
In order to reduce the friction between the well treatment fluid and the bore linings, friction pressure reducing additives have been combined with the treatment fluids and added during pumping so as to reduce pump pressure. For example, a type of well treatment commonly utilized for stimulating hydrocarbon production from a subterranean zone penetrated by a well bore is hydraulic fracturing. Hydraulic fracturing, also referred to as fraccing (or fracking), is used to initiate production in low-permeability reservoirs and re-stimulate production in older producing wells. In hydraulic fraccing, a fluid composition is injected into the well at pressures effective to cause fractures in the surrounding rock formation. Fraccing is used both to open up fractures already present in the formation and create new fractures.
Water soluble polymers can be used as friction reducers in well treatment fluids to alter the rheological properties of the fluid so that the turbulent flow is minimized, thereby preventing consequent energy loss in the fluid as it is pumped through the pipe. These types of treatments are often called “slick water treatments or slick water fracs.” In some instances, water soluble friction reducing polymers are suspended in water in oil emulsions, wherein upon addition to the aqueous treatment fluid, the emulsion must invert to release the friction reducing polymer into the fluid. Performance in the field depends upon the ability of the emulsions to invert, or break, quickly. Certain conditions, for example high brine conditions, can hinder the breaking of the emulsion. In particular, high brines including potassium chloride, sodium chloride, seawater and other API base brines that include calcium or magnesium hardness interfere with the inversion of emulsion polymers such that the emulsions do not break or generate the rheology needed to accomplish superior friction reduction.